This invention relates to shaving systems including a razor handle and a disposable cartridge adapted for releasable attachment to the handle.
In its preferred embodiments, the invention is directed in particular to a shaving system comprising a cartridge having a plurality of sharpened cutting edges arranged in a shaving plane. Such cartridges typically provide a smoother and closer shave than the single blade used in earlier razors, but require special mounting arrangements so as to expose the shaving plane (typically the largest, flat side of the cartridge) for use.
The cutting edges are commonly provided by a plurality of blades arranged between a guard and a cap. The guard and cap are arranged respectively in front of and behind the cutting edges when considered in the direction of shaving, and together with the end portions of the blade housing comprise skin-engaging surfaces serving to determine the position of the cutting edges relative to the user's skin in use. The cutting edges, the guard and the cap lie substantially in alignment within the shaving plane, which is defined as that plane containing the guard and cap or corresponding skin-engaging surfaces in use, while the exposure of each cutting edge (a determinant of the closeness of the shave) is defined as the positive or negative distance of the cutting edge above or below the shaving plane, usually measured in tens of microns.
The cartridge may comprise a plastics housing containing an assembly of two, three, four or more blades, each having a cutting edge. The cap, guard and blades may be fixedly or moveably mounted (e.g. on springs) in the housing, or the cap and guard may be integral parts of the housing. Alternatively the cartridge may comprise an assembly or even a unitary element having a plurality of cutting edges made for example from a single piece of steel, ceramic or silicon material.
Typically, a shaving system also includes a dispenser for holding new cartridges, which is preferably adapted also to receive the used cartridges so as to retain them safely prior to disposal. Preferably, the cartridges are removed from and returned to the dispenser by means of the razor handle, so that the user's fingers are not exposed to the cutting edges.
Many razor handles now available in the market provide a pivoting mechanism in which the pivot axis is arranged on the opposite side of the cartridge from the shaving plane and in-between the guard and the cap, allowing the user to apply force to the cutting edges directly in line with the pivot axis. Such pivot mechanisms help the cartridge to follow the contours of the body area being shaved, but do not effectively limit the force applied to the skin.
The K-4 Tetra Neo™ shaving system manufactured by Kai Corporation of Tokyo, Japan provides a handle having two bars with hooked distal ends which are inserted into apertures in the bottom of the cartridge, providing a pivot axis. A control button is depressible to urge the bars apart so as to detach the cartridge from the handle. The cartridges are retained in a dispenser by flat structures which extend part-way over the bottom side of the cartridge and exert a resilient downward retaining force. The bars are inserted into the cartridge along a first (vertical) axis normal to the dispenser base, following which the cartridge is retracted from the dispenser along a second, inclined axis from beneath the retaining structure.
WO2005/090020 A1 discloses a shaving system having a dispenser formed in two parts and assembled by ultrasonic welding. Each cartridge includes an elastomeric protuberance for retaining it in the dispenser, and a socket attached to the blade housing by a pivoting joint. The handle includes a connection structure for insertion into the socket, with a spring biased retaining assembly having a release button that allows the handle to be disconnected and withdrawn from the socket along the axis of insertion and retraction of the cartridge into and from the dispenser.
Since all three system elements are more or less complex assemblies, the latter system is complicated to manufacture and may present difficulties in cleaning debris from the interstices of the handle and cartridge mechanisms. Some users may find difficulty in manipulating a cartridge release button. Moreover, the cartridge structure when retained in the dispenser presents a confusing array of surfaces and apertures into which the user may attempt to insert the connection structure of the handle, so care is required when changing the cartridge.
The pressure exerted against the user's skin by the cutting edges and by the cap and guard or other skin-engaging surfaces is an important factor in determining the closeness of the shave. If too much pressure is exerted, the shave may be overly aggressive so that the blades irritate or cut the user's skin. If too little pressure is exerted, the shave quality may be poor. It is therefore desirable to provide some means for limiting the pressure of the blades against the skin.
At the same time, the user should be able to exercise precise control over the position of the cartridge and to obtain tactile feedback giving a “feel” for the interaction between the cartridge and the skin via the handle during shaving.
A pivoting connection between the cartridge and the handle helps the shaving plane to remain in correct relation to the skin as it passes over the changing contours of the user's body. However, in practice it can often fail to limit the force applied to the user's skin, since the user may apply force to the cutting edges directly in line with the pivot axis while moving the cartridge in the direction of shaving. At the same time, the pivot mechanism can also make it difficult for the user to control the shaving process and to “feel” the engagement between the cutting edges and the skin through the razor handle, because the rotational position of the handle relative to the cartridge has little or no effect on the pressure of the cartridge against the skin.
GB 2 408 010 A to the present applicant discloses a one-piece razor handle formed as a unitary, two-shot moulding. The handle is bifurcated to form a pair of arms, the cartridge being releasably mounted in fixed relation to the distal ends of the arms by squeezing the arms together and then releasing them so as to engage a hook structure on the end of each arm in a cooperating aperture in the cartridge. Each arm is provided with a living hinge surrounded by an elastomeric material, providing a hinge axis which lies just in front of the guard in the direction of shaving. Pressure applied to the cartridge during shaving causes the cartridge to pivot about the hinge axis with respect to the handgrip against the restoring force of the elastomer, so that the cartridge follows the contours of the user's skin. The position and structure of the hinge effectively limits the pressure applied to the cutting edges while providing the user with tactile feedback that enables precise control of the shaving operation.